No converter found capable of converting from type org.bson.BsonUndefined

Question

I have mongo driver 3.2.2, spring data mongodb 1.9.1.RELEASE.

Collection :

{
  "_id": "5728a1a5abdb9c352cda6432",
  "isDeleted": null,
  "name": undefined
},
{
  "_id": "5728a1a5abdb9c352cda6433",
  "isDeleted": null,
  "name": null
}

When I try to fetch record with {"name":undefined} I get following exception.

org.springframework.core.convert.ConverterNotFoundException: No converter found capable of converting from type org.bson.BsonUndefined to type java.lang.String
    at org.springframework.core.convert.support.GenericConversionService.handleConverterNotFound(GenericConversionService.java:313) ~[spring-core-4.1.7.RELEASE.jar:4.1.7.RELEASE]
    at org.springframework.core.convert.support.GenericConversionService.convert(GenericConversionService.java:195) ~[spring-core-4.1.7.RELEASE.jar:4.1.7.RELEASE]
    at org.springframework.core.convert.support.GenericConversionService.convert(GenericConversionService.java:176) ~[spring-core-4.1.7.RELEASE.jar:4.1.7.RELEASE]
    at org.springframework.data.mongodb.core.convert.MappingMongoConverter.getPotentiallyConvertedSimpleRead(MappingMongoConverter.java:821) ~[spring-data-mongodb-1.7.1.RELEASE.jar:?]

How to solve this? I have multiple types which needs to be converted from BsonUndefined like String, Date, PhoneNumber, etc...

Answer 1

We ran into this issue recently, so I'm putting the results of my research here in case someone else has this issue as well.

This is a known error in Spring Data MongoDB:

https://jira.spring.io/browse/DATAMONGO-1439

The workaround from that link is to add an explicit converter for converting from BsonUndefined to null. For example, using Java 8:

@ReadingConverter
public class BsonUndefinedToNullObjectConverterFactory implements ConverterFactory<BsonUndefined, Object> {
    @Override
    public <T extends Object> Converter<BsonUndefined, T> getConverter(Class<T> targetType) {
        return o -> null;
    }
}

Without the Lambda (pre-Java 8):

@ReadingConverter
public class BsonUndefinedToNullObjectConverterFactory implements ConverterFactory<BsonUndefined, Object> {

    @Override
    public <T extends Object> Converter<BsonUndefined, T> getConverter(Class<T> targetType) {
        return new Converter<BsonUndefined, T>() {
            @Override
            public T convert(BsonUndefined source) {
                return null;
            }
        };
    }
}